Because water falls in the hole, ash floats everywhere. Specifically, water will bring some initial angular momentum due to various disturbances (because the structure of the water tank itself may also give water a moment), and the water leaked from the hole only takes away a small part of angular momentum. With the downward leakage of water, the mass of the whole water body decreases obviously, but the angular momentum decreases not so fast, which leads to the increase of angular velocity and the acceleration of rotation speed of water. Dust does not fall along a fixed axis, so the angular momentum does not change. P. It is often heard that the rotation of water is influenced by Coriolis force, but the influence of Coriolis force can be basically ignored.

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